Ultra-low temperature medium pressure forming method for complex curved-shaped components

ABSTRACT

Disclosed is an ultra-low temperature medium pressure forming method for complex curved-shaped components. The method includes steps of distributing a blank by die closing preforming and forming the complex curved-shaped components by ultra-low temperature medium pressurization, comprising: placing a plate on a female die and tightly pressing the plate by a blank holder; driving a male die to move downwards to make the plate distribute the blank in advance in a large-area mode, thus forming a prefabricated plate blank; filling a cavity with an ultra-low temperature medium to make the prefabricated plate blank be gradually attached to a molded surface of a female die cavity under the pressure action of the ultra-low temperature medium, and thereby forming the complex curved-shaped component; and removing the male die blank holder and taking out the formed complex curved-shaped component.

FIELD OF TECHNOLOGY

The present invention relates to the technical field of plate forming, and in particular relates to an ultra-low temperature medium pressure forming method for complex curved-shaped components.

BACKGROUND

Thin-walled curved-shaped components are the key structures of launch vehicles, aircrafts, high-speed rails, and new energy automobiles, which directly affect the service performance of launch equipment. Such components are not only critical, but also large in demand, accounting for more than 50% of amount in the aircrafts and automobiles. To meet significantly increased service requirements of new generation of equipment, thin-walled curved-shaped components are becoming more and more complex in shape and more difficult to deform the material. For example, to reduce the weight and improve the profile streamline, most of covering parts for the new energy automobile are largely made of high-strength aluminum alloy, and the section shape is a special-shaped curved surface with positive and negative curvatures. To meet the aerodynamic performance of high-speed driving above 300 km/h, a high-speed train nose requires a covering part with small feature ridges, which has small sharp fillets formed in a large-size space curved surface. To meet the requirements of high reliability and air impermeability, a novel aircraft cabin door and a skin type component mostly adopt special-shaped curved components made of high-strength aluminum alloy. Such components are generally special-shaped curved surfaces and have local small fillets or small features, and the ratio of the fillet radius to the wall thickness of the small features is even close to 1.0.

The thin-walled curved-shaped components are generally formed and manufactured by adopting a deep-drawing process; actually, a plate is plastically deformed under the action of a male die and is continuously drawn into a gap between the male die and a female die to form a part. The final shape of the component is decided by pressing of the male die or matched pressing of the male and the female die. For the component with relatively simple curved shape, the component can be directly formed through deep-drawing, such as a conventional automobile covering part, an airplane door surrounding frame and the like; for the component with a complex curved shape or large depth, complex procedures such as multi-pass pre-forming and intermediate annealing and the like are needed to form the component, resulting in the problems of low yield and poor quality of finished products; for a complex curved-shaped components with positive and negative curvatures or local small features, due to successive contact sequence of the plate and the forming die and the matching of the male die and the female die, cracking is prone to occurring at a transition or local fillet, and forming cannot be completed smoothly; more importantly, the normal-temperature formability of the high-strength aluminum alloy is relatively poor (the formability is less than 10%), which is more likely to cause cracking defects and exceeds the limit of deep-drawing forming of the high-strength aluminum alloy. At present, the problem of forming cracking of the high-strength aluminum alloy complex curved-shaped components still cannot be solved.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide an ultra-low temperature medium pressure forming method for complex curved-shaped components to solve the problem in the prior art, thus an aluminum alloy plate deforms under an ultra-low temperature condition, the problem of forming cracking of the complex curved-shaped components can be avoided, and the wall thickness uniformity and the forming efficiency are improved.

To achieve the objective, the present invention provides the following solutions:

An ultra-low temperature medium pressure forming method for complex curved-shaped components, comprising: distributing a blank by die closing preforming and forming the complex curved-shaped components by ultra-low temperature medium pressurization, includes steps as follows:

S1, placing a plate on a female die, and applying a blank holding force to a blank holder to make the blank holder press the plate tightly;

S2, driving a male die to move downwards to make the plate distribute the blank in advance in a large-area mode under the action of the female die and the male die, forming a prefabricated plate blank, wherein the female die and the male die are mismatched in molded surfaces; adjusting the blank holding force on the blank holder according to a deep-drawing depth of the plate to guarantee that a cavity between the prefabricated plate blank and the male die is kept in a sealed state;

S3, filling the cavity between the prefabricated plate blank and the male die with an ultra-low temperature medium through a booster pump and a circulation pipeline, and enabling the prefabricated plate blank to be gradually attached to the molded surface of the female die under the pressure action of the ultra-low temperature medium, t forming the complex curved-shaped component; and

S4, recycling the ultra-low temperature medium in the cavity, driving the male die to move upwards, removing the blank holder, and taking out the formed complex curved-shaped component.

Preferably, the male die is a cambered die in smooth transition, and a molded surface with a complex shape is arranged in the female die.

Preferably, before step S1, the male die is cooled to a set temperature of lower than −160° C.

Preferably, a solution cavity for accommodating the ultra-low temperature medium is arranged in the male die, and the solution cavity is communicated with a low-temperature vessel and the booster pump through a circulation path, wherein the low-temperature vessel is used for placing the ultra-low temperature medium.

Preferably, pressurization pressure of the booster pump is no more than 100 MPa.

Preferably, a sealing element is arranged at a contact position of an upper surface of the blank holder and the male die, the blank holder applies a unit blank holding force of less than 5 MPa in step S1, and the blank holder applies a unit blank holding force of more than 7 MPa after being adjusted in step S2.

Preferably, the die closing preforming step in step S2 is omitted, the blank holder is replaced with a flat plate shape from a hollow ring shape, the ultra-low temperature medium serving as the male die is directly pressurized into the sealed cavity through the booster pump, the plate is subject to pre-deep-drawing to distribute the blank, then the pressure of the ultra-low temperature medium in the sealed cavity is increased to make the plate be gradually attached to the molded surface of the female die, thus forming the complex curved-shaped component.

Preferably, circulation pipelines communicated with the ultra-low temperature medium are respectively provided on the middle of the flat plate shaped blank holder and the female die, and a sealed cavity is kept to be formed between the blank holder and the female die.

Preferably, the ultra-low temperature medium is liquid nitrogen, liquid argon, or liquid helium.

Preferably, the plate is a rolled aluminum alloy plate having a wall thickness of 0.1-10 mm, and the plate is Al—Li alloy, Al—Cu alloy, Al—Mg—Si alloy, or Al—Zn alloy.

Compared with the prior art, the present invention obtains the following technical effects:

In the present invention, an aluminum alloy plate deforms under the ultra-low temperature condition, the forming performance is remarkably improved, and the problems that high-strength aluminum alloy is poor in normal-temperature forming plasticity and prone to cracking are solved. The blank is distributed through die closing preforming, and the complex curved-shaped surface is formed through ultra-low temperature medium pressurization, and the blank is optimally distributed according to the shape of a component, thus local cracking can be avoided, and the wall thickness uniformity is improved. By pressurizing the plate with the ultra-low temperature medium, direct cooling of the plate can be achieved, and complex molded surface matching between the male die and the female die can also be avoided, facilitating the forming of the complex curved-shaped components.

BRIEF DESCRIPTION OF THE DRAWINGS

To illustrate the technical solutions in the embodiments of the present invention or in the prior art more clearly, the following briefly introduces the accompanying drawings required for describing the embodiments. Apparently, the accompanying drawings in the following description show merely some embodiments of the present invention, and those of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative efforts.

FIG. 1 is a diagram I of an ultra-low temperature medium pressure forming method for complex curved-shaped components in accordance with the present invention;

FIG. 2 is a diagram II of an ultra-low temperature medium pressure forming method for complex curved-shaped components in accordance with the present invention;

FIG. 3 is a diagram III of an ultra-low temperature medium pressure forming method for complex curved-shaped components in accordance with the present invention;

FIG. 4 is a diagram IV of an ultra-low temperature medium pressure forming method for complex curved-shaped components in accordance with the present invention;

FIG. 5 is a diagram V of an ultra-low temperature medium pressure forming method for complex curved-shaped components in accordance with the present invention;

wherein, 1—female die; 2—plate; 3—blank holder; 4—ultra-low temperature medium; 5—male die; 6—prefabricated plate blank; 7—complex curved-shaped components; 8—sealing element; 9—booster pump; 10—ultra-low temperature vessel; 11—circulation pipeline.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are merely a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

An objective of the present invention is to provide an ultra-low temperature medium pressure forming method for complex curved-shaped components to solve the problem in the prior art. The aluminum alloy plate deforms under an ultra-low temperature condition, thus the problem of forming cracking of the complex curved-shaped components can be avoided, and the wall thickness uniformity and the forming efficiency are improved.

To enable the above objective, features and advantages of the present invention to be more apparent and easily understood, the present invention is further illustrated below with reference to the accompanying drawings and embodiments.

Embodiment 1

As shown in FIG. 1 to FIG. 5, the embodiment provides an ultra-low temperature medium pressure forming method for complex curved-shaped components, a blank is distributed through die closing preforming, and a complex curved-shaped component 7 is formed through ultra-low temperature medium pressurization. The plate 2 is a rolled aluminum alloy plate having a wall thickness of 0.1-10 mm, and the plate 2 is Al—Li alloy, Al—Cu alloy, Al—Mg—Si alloy, or Al—Zn alloy, including steps as follows:

S1, the plate 2 is placed on a female die 1, a blank holding force is applied on the blank holder 3 to make the blank holder 3 press the plate 2 tightly; before that, cooling a male die 5 is cooled to a set temperature of lower than −160° C.

S2, the male die 5 is drove to move downwards to make the plate 2 distribute the blank in advance in a large-area mode under the action of the female die 1 and the male die 5, thereby forming a prefabricated plate blank 6, wherein the female die 1 and the male die 5 are mismatched in molded surfaces, and the male die 5 is in contact with the edge of the prefabricated plate blank 6, the male die 5 is a cambered die in smooth transition, and a molded surface with complex shape is arranged in the female die 1. The blank holding force on the blank holder 3 is adjusted according to a deep-drawing depth of the plate 2 to guarantee that a cavity between the prefabricated plate blank 6 and the male die 5 is kept in a sealed state. The sealing element 8 is arranged at the contact position of the upper surface of the blank holder 3 and the male die 5 to guarantee the sealing performance of the cavity. The blank holder 3 applies a unit blank holding force of less than 5 MPa in step S1, and the blank holder 3 applies a unit blank holding force of more than 7 MPa after being adjusted in step S4.

S3, the cavity between the prefabricated plate blank 6 and the male die 5 is filled with an ultra-low temperature medium 4 through the booster pump 9 and the circulation pipeline 11, and the prefabricated plate blank 6 is enabled to be gradually attached to the molded surface of the female die 1 under the pressure action of the ultra-low temperature medium 4, thereby forming the complex curved-shaped components.

S4, the ultra-low temperature medium 4 in the cavity is recycled, the male die 5 is drove to move upwards, the blank holder 3 is removed, and the formed complex curved-shaped component 7 is took out. The ultra-low temperature medium 4 is liquid nitrogen, liquid argon, or liquid helium. A solution cavity for accommodating the ultra-low temperature medium 4 is arranged in the male die 5, and the solution cavity is communicated with a low-temperature vessel 10 and the booster pump 9 through a circulation path, wherein the low-temperature vessel 10 is used for placing the ultra-low temperature medium 4; and the pressurization pressure of the booster pump 9 is no more than 100 MPa.

The die closing preforming step in step S2 is omitted, the blank holder 3 is replaced with a flat plate shape from a hollow ring shape, the ultra-low temperature medium 4 serving as the male die 5 is directly introduced by pressurizing the sealed cavity through the booster pump 9, the plate 2 is subject to pre-deep-drawing to distribute the blank, then the pressure of the ultra-low temperature medium 4 in the sealed cavity is increased to enable the plate 2 to be gradually attached to the molded surface of the female die 1, thus forming the complex curved-shaped component. Circulation pipelines 11 communicated with the ultra-low temperature medium 4 are respectively provided on the middle of the flat plate shape blank holder 3 and the female die 1, and a sealed cavity is kept to be formed between the blank holder 3 and the female die 1.

Embodiment 2

As shown in FIG. 1 to FIG. 3, a blank in the embodiment is an aluminum alloy plate in a solid solution state 7075, having a thickness of 1.5 mm, a length of 1200 mm, and a width of 800 mm. The complex curved-shaped component 7 is a box-shaped part, an opening of that has a length of 900 mm, a width of 600 mm, and a maximum depth of 150 mm, and the bottom of the complex curved-shaped component has a complex varying radius of curvature and has a local concave feature. The blank is distributed by rigid die pre-deep-drawing, then the ultra-low temperature medium 4 is introduced for cooling and pressurized forming, including steps as follows:

S1, the aluminum alloy plate 2 is placed on a female die 1, and a blank holding force is applied to close a blank holder 3.

S2, a set blank holding force is applied on the blank holder 3, a male die 5 is moved downwards to a set depth 120 mm to make the plate 2 distribute the blank in advance in a large-area mode under the action of a rigid die; the deep-drawing and blank holding force are adjusted to make an outer flange of the male die 5 press a sealing element 8 installed on the blank holder 3 tightly and the blank holder 3 press a prefabricated plate blank 6 tightly to guarantee that a cavity between the prefabricated plate blank 6 and the male die 5 is effectively sealed.

S3, the cavity between the prefabricated plate blank 6 and the male die 5 is filled with liquid nitrogen serving as the ultra-low temperature medium 4, to cool the prefabricated plate blank 6 to be lower than −160° C.

S4, the pressure of the ultra-low-temperature medium 4 is increased to 80 MPa, and the prefabricated plate blank 6 is formed a complex curved-shaped surface under the pressure action of the ultra-low temperature medium 4.

S5, the ultra-low temperature medium 4 in the cavity is recycled, the male die 5 and the blank holder 3 are drawn back, and the formed complex curved-shaped component 7 is taken out.

The ultra-low temperature medium 4 in the embodiment may also adopt the liquid argon.

In the embodiment, the blank is distributed through die closing preforming, then the complex curved-shaped surface can be formed by pressurization of ultra-low temperature medium 4; the blank is optimally distributed according to the shape of the component, and local cracking can be avoided and the wall thickness uniformity can be improved. The ultra-low temperature medium 4 is not only used for pressurizing, but also for cooling. The aluminum alloy plate deforms under the ultra-low temperature condition, the forming performance is obviously improved and the problem of forming cracking of the high-strength aluminum alloy complex curved-shaped component 7 is avoided.

Embodiment 3

As shown from FIG. 1 to FIG. 3, a blank in the embodiment is an aluminum alloy plate in a solid solution state 2195, having a thickness of 1.0 mm and a diameter of 1200 mm. The complex curved-shaped component 7 is a deep-cavity multi-way part with an opening diameter of 600 mm and a sidewall depth of 575 mm, the bottom of the complex curved-shaped component is a special-shaped curved surface having a maximum depth of 600 mm, and the sidewall has four convex features. The blank is distributed by conducting pre-deep-drawing to the maximum extent by means of rigid die pre-cooling, and then an ultra-low temperature medium 4 is introduced for cooling and pressurized forming of the blank, including steps as follows:

S1, liquid nitrogen is used as the ultra-low temperature medium 4, firstly a male die 5 is cooled to a temperature of lower than −180° C., wherein a solution cavity for circulating the ultra-low temperature medium 4 is arranged in the male die 5.

S2, the aluminum alloy plate 2 is placed on a female die 1, and a blank holding force is applied to close a blank holder 3.

S3, a unit blank holding force of 3 MPa is applied to the blank holder 3, the male die 5 is moved downwards to a set depth of 575 mm to make the plate 2 be deep-drawn under the condition of lower than −160° C. to form a vertical wall cylinder; the unit pressure of the deep-drawing and the blank holder are increased to 7 MPa to make an outer flange of the male die 5 press a sealing element 8 installed on the blank holder 3 tightly, then the plate 2 is pressed tightly by the blank holder 3 to guarantee that a cavity between the plate 2 and the male die 5 is effectively sealed.

S4, the cavity between the plate 2 and the male die 5 is filled with the ultra-low temperature medium 4 to cool the plate 2 to be lower than 180° C.; the pressure of the ultra-low temperature medium 4 in the cavity is increased to 60 MPa to enable the plate 2 to form convex features on the sidewall and a complex shape of the special-shaped curved surface at the bottom under the pressure action of the ultra-low temperature medium 4.

S5, the ultra-low temperature medium 4 in the cavity is recycled, the male die 5 and the blank holder 3 are drawn back, and the formed complex curved-shaped component 7 is taken out.

In the embodiment, the blank is distributed through die closing preforming, then the complex curved-shaped surface can be formed by pressurization of ultra-low temperature medium 4; the blank is optimally distributed according to the shape of the component, and local cracking can be avoided, and the wall thickness uniformity can be improved. The plate 2 is pre-formed under the ultra-low temperature condition by pre-cooling a rigid die, the blank distribution degree through preforming can be obviously improved, and the forming limit is improved. The ultra-low temperature medium 4 is not only used for pressurizing, but also for cooling. The aluminum alloy plate deforms under the ultra-low temperature condition, the forming performance is obviously improved and the problem of forming cracking of the high-strength aluminum alloy complex curved-shaped component 7 is avoided.

Embodiment 4

As shown from FIG. 4 to FIG. 5, a blank in the embodiment is an aluminum alloy plate in a solid solution state 6016, having a thickness of 1.0 mm and a diameter of 1000 mm. The complex curved-shaped component 7 is a special-shaped curved surface part with an opening diameter of 600 mm and the maximum depth of 300 mm, and the bottom of the complex curved-shaped component is a doublet special-shaped curved surface having a deep concave feature. The plate 2 is cooled through an ultra-low temperature medium 4, a blank holding force is controlled to conduct deep-drawing by using the ultra-low temperature medium 4 as a flexible male die to distribute the blank, and then the pressure of the ultra-low temperature medium 4 is increased to form complex local features, including steps as follows:

S1, the aluminum alloy plate 2 is placed on a female die 1, the blank holding force is applied to close a blank holder 3, wherein the blank holder is flat-plate-shaped.

S2, the cavity between the plate 2 and the blank holder is filled with liquid nitrogen serving as the ultra-low temperature medium 4, and the plate 2 is cooled to a temperature of lower than −160° C.

S3, the blank holding force is applied on the blank holder 3, the pressure of the ultra-low temperature medium 4 in the cavity between the plate 2 and the blank holder is increased to 10 MPa, thus the plate 2 is deeply drawn to a large-area special-shaped curved surface under the pressure action of the ultra-low temperature medium 4.

S4, the blank holding force is increased to make an upper cavity be sufficiently sealed, then the pressure of the ultra-low temperature medium 4 is increased to 40 MPa to enable the plate 2 to form local features in a bulged manner under the pressure action of the ultra-low temperature medium 4 until all shapes are formed.

S5, the ultra-low temperature medium 4 in the cavity is recycled, the blank holder 3 is drawn back, and the formed complex curved-shaped component 7 is taken out.

The aluminum alloy plate of the embodiment always deforms under the ultra-low temperature condition, the forming performance is obviously improved, and the problems of poor plasticity and easy cracking in normal-temperature forming of a high-strength aluminum alloy are avoided. The blank is distributed through preforming of the ultra-low temperature medium 4, thus the blank optimization degree by preforming is improved, and the limitation of distribution of the blank by the rigid die is avoided. The blank is optimally distributed according to the shape of the component, the local cracking can be avoided, and the wall thickness uniformity can be improved. The ultra-low temperature medium 4 not only can achieve direct cooling of the plate 2, but also can be pressurized to form a complex feature, the complex molded surface or gap matching difficulty between the male die 5 and the female die 1 is reduced, facilitating the forming of the complex curved-shape component 7.

Specific examples are used for illustration of the principles and embodiments of the present invention in the specification. The description of the embodiments is merely used to help illustrate the method and its core principles of the present invention. Meanwhile, those of ordinary skill in the art can make various modifications in terms of specific embodiments and scope of application in accordance with the thoughts of the present invention. In conclusion, the content of this specification shall not be construed as a limitation to the present invention. 

What is claimed is:
 1. An ultra-low temperature medium pressure forming method for complex curved-shaped components, comprising distributing a blank by die closing preforming and forming the complex curved-shaped components by ultra-low temperature medium pressurization, wherein comprises steps as follows: S1, placing a plate on a female die, and applying a blank holding force to a blank holder to make the blank holder press the plate tightly; S2, driving a male die to move downwards to make the plate distribute the blank in advance in a large-area mode under the action of the female die and the male die, forming a prefabricated plate blank, wherein the female die and the male die are mismatched in molded surfaces; adjusting the blank holding force on the blank holder according to a deep-drawing depth of the plate to guarantee that a cavity between the prefabricated plate blank and the male die is kept in a sealed state; wherein a sealing element is arranged at a contact position of an upper surface of the blank holder and the male die, the blank holder applies a unit blank holding force of less than 5 MPa in step S1, and the blank holder applies a unit blank holding force of more than 7 MPa after being adjusted in step S2; S3, filling the cavity between the prefabricated plate blank and the male die with an ultra-low temperature medium through a booster pump and a circulation pipeline, and enabling the prefabricated plate blank to be gradually attached to the molded surface of the female die under the pressure action of the ultra-low temperature medium, forming the complex curved-shaped component; and S4, recycling the ultra-low temperature medium in the cavity, driving the male die to move upwards, removing the blank holder, and taking out the formed complex curved-shaped component.
 2. The ultra-low temperature medium pressure forming method for complex curved-shaped components according to claim 1, wherein the male die is a cambered die in smooth transition, and a molded surface with complex shape is arranged in the female die.
 3. The ultra-low temperature medium pressure forming method for complex curved-shaped components according to claim 1, wherein, before step S1, the male die is cooled to a set temperature of lower than −160° C.
 4. The ultra-low temperature medium pressure forming method for complex curved-shaped components according to claim 1, wherein a solution cavity for accommodating the ultra-low temperature medium is arranged in the male die, and the solution cavity is communicated with a low-temperature vessel and the booster pump through a circulation path, wherein the low-temperature vessel is used for placing the ultra-low temperature medium.
 5. The ultra-low temperature medium pressure forming method for complex curved-shaped components according to claim 4, wherein pressurization pressure of the booster pump is no more than 100 MPa.
 6. The ultra-low temperature medium pressure forming method for complex curved-shaped components according to claim 1, wherein the ultra-low temperature medium is liquid nitrogen, liquid argon, or liquid helium.
 7. The ultra-low temperature medium pressure forming method for complex curved-shaped components according to claim 1, wherein the plate is a rolled aluminum alloy plate having a wall thickness of 0.1-10 mm, and the plate is Al—Li alloy, Al—Cu alloy, Al—Mg—Si alloy, or Al—Zn alloy. 